Normal labs but am symptomatic

Hi all! I am new to the forum. Diagnosed with Hashimoto's 10 years ago. On & off thyroid meds but more off because of weight gain. Currently on generic Levoxyl for three months. Have gained approx 30 lbs. No other changes except giving up diet pop. I have abnormal cramping and edema in my extremities and it feels like someone has their hands around my neck. TSH = 1, T3 & T4 are within normal range. I have not had antibodies checked but it's next on my list. Part of me thinks that the weight gain is from the meds not working (no T3) while another part of me thinks that the symptoms are from aspartame toxicity. May be a combo of both. Has anyone had a similar experience?